Reversing-key



(No Model.)

, E. A. COLBY. REVERSING KEY.

No. 442,800. Patented Dec. 16. 1890.

WITNESSES:

ATTORNEY.

UNITED STATES PATE T OFFICE.

EDlVARD A. COLBY, OF NEWARK, NElV JERSEY.

REVERSlNG-KEY.

SPECIFICATION forming part of Letters Patent No. 442,800, dated. December 16, 1890.

Application filed February 28, 1890. Serial No. 342,123. (No model.)

To all whom it may concern:

Be it 'known that I, EDWARD A. COLBY, of Newark, Essex county, New Jersey, have invented a new and useful Improvement in Reversing-Keys, of which the following is a specification.

My invention relates to a reversing-key or commutator for reversing the direction of an electrical current passing through a conductor; andit consists in the construction and arrangement of said key, and also in the combination of said key with an electrical meastiring-instrument.

The form of measuring instrument with which I here show my reversing-key combined is that patented to Edward Weston by Letters Patent-No. 392,387, November 6,1888, the said instrument being a voltmeter in which a coil of wire is suspended, so as to rotate between the poles of a magnet, and which coil, in

accordance with well-known laws, takes certain angular positions, depending upon the electro-motive force of the current passing through it. By means of the combination of my key with the aforesaid instrument I am enabled to reverse the current through the rotating coil without effecting a corresponding change in the direction of the current through a fixed resistance-coil also contained in the instrument.

In the accompanying drawings, Figure 1 is a diagram illustrating the combination of my reversing-key with a measuring-instrument of the type above referred to. Fig. 2 is a bottom View of my apparatus, and Fig. 3 is a similar view showing the contacts when the key is in different positions. Fig. 4: is a sectional view on the line X X. of Fig. 2.

Similar letters of reference indicate like parts.

A represents the base or support in which the key is arranged. Through said support is made a cylindrical opening B, which at its lower port-ion G is enlarged so that a shoulder is formed, to which shoulder are secured the four fixed segmental metal plates E F G H. These plates are insulated from one another, and to them respectively are connected the circuit-terminals a b c d.

In the cylindrical opening B in the support A is secured a flanged sleeve or bushing I of insulating material, and in said sleeve is made a slot J ninety degrees in length.

L is the key in the form of a pin provided with a head or flange resting on the upper edge of the sleeve I, and having a shank M,

with a downward projection N, to opposite sides of which are secured the forked contactpieces 0 and P. The pieces 0 and P are springplates of metal, and each piece has two projections e f and g h, which projections bear against the inner edges of the fixed contactpieces E F G H.

In the periphery of the shank M is a stop Q, which is received in the quadrantal slot J. The rotary motion of the key L is therefore limited, and cannot extend over a distance beyond ninety degrees, because the stop Q then meets the ends of the slot J.

Referring now to Fig. 2, it will be evident that when the pin is turned in the position there shown a current entering in the direction of the arrow Z will pass first to. plate H, to contact-arm g, to contact-arm h, to plate G, to wire I), and thence, if connection be made between wires a and b, to plate E, contact-arms f e, plate F, and wire 0. If, however, the key be turned into the position shown in Fig. 3,then the current entering by the wire d, (indicated, as before, by the arrow 1,) will pass to plate H, to contact-arm h, contact-arm plate F, wire 0, and then if wires or and c be connected to wire a, plate E, contact-arm e, contact-arm f, fixed contact-plate G, and wire 12.

Referring now to Fig. 1, A represents the permanent magnet of the apparatus set forth in the above-named patent to Edward Weston.

B C are the pole-pieces. D is the fixed cyl inder. E is the rotating coil moving in the annular space between the cylinder D and the pole-pieces B C. F is the fixed resistance-coil, and G H are binding-posts. Assuming the key to be in the position shown in Fig. 2 and the current to enter at the binding-post II, the current will then pass from plate H to plate G, through the wire I) to the coil E, and thence back by wire 0 to plate F to plate E, and so by wire a to resistance-coil F, and thence to binding-post G. If, howplate Fby wire 0 to coil E, and by wire Y) to plate G, then to plate E, and thence by wire a to resistance-coil Fand binding-post G.

It Will be seen from the foregoing that the direction of the current in the coil E and wire I) c is reversed, while in both cases it remains the same in direction through the wire a and resistance-coil F.

The object of reversing the current only through the movable coil instead of through both movable coil and the resistance coil of the instrument is to make the difference of potential between the contact-plates of the reversing-key very small, so as to avoid the danger of short-cireuiting due to the presence of metallic dust, for example, between said contact-plates.

In a measuring-instrument ot' the character illustrated the diiterence of potential between the terminals of the coil may be but three-quarters of a volt, while the difference of potential at the binding-post of the instrument, the resistancecoil then beingincluded in the circuit, may be perhaps three hundred volts or more.

I elaim- 1. The combination of the support A, havplates.

2. In an electrical measuring-instrument, the combination of the vibrating coil E, contact-plates F and G, connected to the terminals of said coil, contact-plate E, a fixed resistanee-coil F, having one terminal connect; ed to said plate E, contact-plate II, (the said contact-plates being insulated from one an other,) rotary key L, and bifurcated contactarms 0 P on opposite sides of said pin, insulated from one another and making contact with said plates E F G H.

EDXVARD A. COLBY.

Vitnesses:

JAMES S. GREvEs, M. Boson. 

